A tensile test used to study deformation and other characteristics of a metallic material is a typical objective evaluation method but requires cutting a test piece off a bulk specimen, which makes the test highly invasive and makes it difficult to apply the test to the material of which a product is made and living biological tissue.
On the other hand, an indentation test also typically used in material hardness measurement allows noninvasive measurement because the test does not require cutting a test piece off a bulk specimen. It has been known in an indentation test that the Hertzian elastic contact theory can be used with metallic materials in a highly reliable manner (see Non-Patent Document 1, for example).
There have also been several indentation tests used to measure characteristics of a soft material that involves large deformation, such as biological soft tissue (see Non-Patent Documents 2 to 5, for example).
The present inventors have disclosed technical details associated with the invention (see Non-Patent Documents 6 to 9, for example).